1. Field of the Invention
The present invention relates to a method of forming a trench in a semiconductor substrate, and more particularly, to a method of forming an ultra-narrow trench in a semiconductor substrate.
2. Description of the Prior Art
In semiconductor manufacturing processes, in order to transfer an integrated circuit layout onto a semiconductor wafer, the integrated circuit layout is first designed and formed as a photo-mask pattern. The photo-mask pattern is then proportionally transferred to a photoresist layer positioned on the semiconductor wafer. This is so called lithography technology.
As the continuous improvement, the current lithography techniques no longer meet the requirements for the reduced dimension of the product devices. For example, in a conventional damascene process for forming a metal interconnection system, a trench pattern is first formed in a hard mask layer, following by a dry etching process to transfer the trench pattern into a dielectric layer by using the hard mask layer as a mask. A metal layer is subsequently filled into the trench in the dielectric layer to form a metal conductive line. However, the width of the trench can not be further reduced due to the limitation of the lithography technology, and the whole dimension of the metal interconnection system and the integration circuit can not be reduced as well.
Therefore, there is still a need for a novel method of forming an ultra-narrow trench in a semiconductor substrate.